A variety of techniques are used for cooling enclosed electronic equipment to maintain a predetermined temperature range for the components included therein. These techniques include providing ventilation in the enclosure to allow heat to escape, improving radiation properties of surfaces to increase the radiation of heat away from the enclosure, adding fans to force cooler air from outside the enclosure across the components therein and thereby to force heat out of the enclosure, using liquid fluid flow through, for example, “cold plates” which are placed on hot components in the enclosure in order to remove heat from those components.
Enclosed telecommunications equipment is one example of electronic equipment typically requiring forced air or liquid cooling. Many electronic boards that are used in rack-mount telecom chassis and many small form factor electronic enclosures, such as 1 U-high servers, have a few components that generate a majority of the heat. Examples are power amplifiers on a radio module and microprocessors in a 1 U-high server or an ATCA (Advanced Telecom Computing Architecture) board.
Currently in most electronic equipment, two different cooling approaches are used; pure air-cooled systems or hybrid-cooled systems. In pure air-cooled systems, all components are cooled by traditional air-cooled heat sinks. To sufficiently cool a few high power components, very high airflow rates and/or large and/or expensive heat sinks are needed. A high airflow rate is usually accomplished by using either large fans or high speed fans. However, this may have a cost and/or noise impact, since large fans are typically more expensive and high speed fans are typically noisy. Further, the high airflow required for cooling the high power density components may be much more than what is necessary for cooling the remainder of the electronics inside the system. Another limitation of this brute-force air cooling technique is that the cooling capacity does not increase proportionally as the airflow rate increases; in fact the improvement in cooling capacity becomes smaller and smaller as the rate of airflow keeps increasing.
Generally, a shortcoming of pure air-cooled systems is that the cooling capacity is limited by the allowable acoustic noise level emitted from the chassis. Further, the increase in cooling capacity diminishes as airflow rate increases. Accordingly, this may sometimes require significant increase in airflow rate and noise level to meet cooling requirements. Further, fans may be operating at high ambient temperatures if they are mounted at exhaust, which may reduce the service life of the fans. And finally, in many cases, the airflow required to cool a few high power dissipating components is disproportionably higher than the airflow that is needed to cool other components in the system.
Current liquid-cooled or hybrid-cooled solutions come in two varieties: those with the entire liquid loop and the fans inside the enclosure; and those with part of the liquid loop located outside of the enclosure and the remainder of the liquid loop plus the fans located inside the enclosure. In the latter case, some manual piping work is needed during installing and removing the equipment or board.
For systems that contain the entire liquid-loop (including the heat exchanger and pump) inside the enclosure, there is no liquid line coming into or out of these enclosures. As far as someone outside of these chassis is concerned, they appear to be air-cooled as cold air enters and hot air exits such chassis. Internally, these chassis are hybrid-cooled chassis since some of the components therein are cooled by cold-plates of the liquid cooling system, while other components are cooled by air with or without heat sinks. The fans that push air through the heat exchanger of the liquid cooling system and/or cool other air-cooled electronics, are inside the chassis as well.
A second group of liquid-cooled or hybrid-cooled chassis is those that receive cooling liquid from outside the enclosure and send the coolant liquid, after it absorbs heat from hot components, outside the chassis for cooling. The heated coolant liquid from the chassis, possibly mixed with the heated coolant liquid coming from other chassis, is circulated through an outside heat exchanger or a chiller that cools the coolant before the coolant returns to the chassis. These chassis usually require extensive piping work during installation or removal. If these chassis are hybrid-cooled, they each will include their own fans.
The shortcomings of existing liquid or hybrid-cooled systems includes the number of moving parts (such as fans and pumps) inside a rack increases proportionally to the number of electronics enclosures in the rack. This will reduce the reliability of the enclosure and rack in general. In addition, each individual enclosure has to use smaller size pumps, fans, and heat exchangers such that the components will fit inside the enclosures. In general, smaller fans and pumps are less efficient than larger ones. If part of the liquid loop is outside the enclosure, there is typically piping work involved to install or remove an enclosure from a rack.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.